Examples of the compound having naphthalene skeleton and anthranilic acid skeleton at the same time are those disclosed in the specification of JP-A 1-287066 (hereinunder, JP-A means “Japanese Unexamined Patent Application”). The specification describes compounds such as N-(2-naphthoyl)anthranylbenzoic acid and shows that these compounds have antiallergic activity or 5-lipoxygenase inhibiting activity. However, these compounds consist of a bicyclic aromatic ring derivative substituted by hydroxyl group or alkoxy group and directly bonded to an anthranilic acid skeleton through an amide bond, and there is no description or suggestion in the specification whether these compounds have cytotoxic action or IgE antibody production suppressing action or not.
Compounds having naphthalene skeleton and anthranilic acid skeleton and exhibiting antiallergic activity and IgE antibody production suppressing activity are described in the specifications of JP-A 1-106818, International Application WO90/12001 and JP-A 7-285858. However, these compounds are different from the compound of the present invention because there is no compound having a principal skeleton containing three aromatic rings at the same time in these compounds.
International Application WO95/32943 and a document “Journal of Medicinal Chemistry (J. Med. Chem.) vol. 40, No. 4, sections 395-407 (1997)” describe compounds having naphthalene skeleton and anthranilic acid skeleton and exhibiting antiallergic activity and IgE antibody production suppressing activity. Further, International Application WO97/19910 describes compounds having benzene skeleton and anthranilic acid skeleton and exhibiting antiallergic activity and IgE antibody production suppressing activity. However, these compounds are also different from the compound of the present invention because the substituent corresponding to the side chain of benzene skeleton or naphthalene skeleton is limited to alkoxy groups, alkenyloxy groups or aralkyloxy groups. Furthermore, the specification merely describes the presence of antiallergic activity and IgE antibody production suppressing activity in these compounds having the above specific substituents.
Compounds having pyridine ring skeleton and anthranilic acid skeleton and exhibiting antibacterial activity are described in the specification of International Application WO95/25723. The specification further describes that the substituent of the pyridine ring includes phenyloxy group and phenylthio group which may have substituents. However, there is no detailed explanation on the kind of the substituents. In the compounds of the present invention, for example, the pyridine ring is always substituted by phenyloxy group, phenylthio group, phenylsulfonyl group, phenylsulfinyl group, phenylcarbonyl group, phenylmethyl group, naphthyloxy group, naphthylthio group, naphthylsulfonyl group, naphthylsuifinyl group, naphthylcarbonyl group or naphthylmethyl group and furthermore the phenyl group or the naphthyl group constitutes the mother nucleus and always substituted by alkoxy group, aryloxy group, etc., which may contain hetero-atoms and, accordingly, the compound of the present invention is different from the compounds described in the above specification. Further, there is no comment on the IgE antibody production suppressing activity in the specification.
Meanwhile, the creation of a new compound having strong cytotoxic action is extremely important in the development of an excellent carcinostatic agent. Since the carcinostatic activity and carcinostatic spectrum of a compound are highly dependent upon its chemical structure in general, it is highly possible to enable the development of a carcinostatic agent having excellent characteristics compared with conventional carcinostatic agents practically in use at present from a cytotoxic compound having a new structure different from the structure of known compounds.
Examples of known low-molecular compound having benzene skeleton or aryl skeleton and exhibiting cytotoxic activity are substituted phenylsulfonyl derivative (JP-A 5-9170), 2-arylquinolinol derivative (JP-A 7-33743) and benzoylacetylene derivative (JP-A 7-97350).
However, the fact that a compound having benzene skeleton or aryl skeleton together with anthranilic acid skeleton has cytotoxic activity or carcinostatic activity is utterly unknown.
The object of the present invention is to provide a new compound usable as a clinically applicable therapeutic agent for cancer and preventive and/or therapeutic agent for allergic diseases.